Apparatus for cooling heat generating spot of electronic device, cooling method therefore, and liquid crystal projector apparatus

ABSTRACT

A silent cooling apparatus for effectively reducing the operating temperature of an electronic device includes a plurality of components which include surfaces opposite to each other with a spacing therebetween and have a heat generating spot on at least any of the surfaces opposite to each other, in a small and low-cost configuration. The apparatus for cooling a heat generating spot of an electronic device includes a cooling apparatus for forcedly air-cooling a heat generating spot of an electronic device which includes a plurality of components which are disposed side by side to have the same in-plane direction, and include heat generating spots within their surfaces. The cooling apparatus includes a first air cooling unit for feeding an air stream to the heat generating spot in an orientation of the in-plane direction, and a second air cooling unit for feeding an air stream to the heat generating spot in the in-plane direction in a different orientation from the air stream by the first air cooling unit.

TECHNICAL FIELD

The present invention relates to an apparatus for cooling a heatgenerating spot (area) of an electronic device, a cooling methodtherefor, and a liquid crystal projector apparatus, and moreparticularly, to an apparatus for cooling a heat generating spot (area)of an electronic device, with two cooling units which feed air streamsthat collide with each other on a cooling plane, a cooling methodtherefor, and a liquid-crystal projector apparatus which includes theapparatus for cooling a heat generating spot of an electronic device.

BACKGROUND ART

Apparatuses for cooling heat generating spots of electronic devices havebeen used in a variety of forms, and cooling apparatuses which rely onair for cooling have been developed in a variety of configurations forpurposes of simplifying the configuration. A plurality of forced aircooling type cooling apparatuses are provided in projector apparatuseswhich are projection display devices currently widely used for businessand home applications.

A projection display device projects an image generated on an imagedisplay element of an image display onto a screen under magnification.Among such projection display devices, a liquid crystal projectorapparatus which employs liquid crystal panels for image display elementsdisplays an image on a screen in the following configuration andoperation.

White light from a light source is reflected by a reflector, and ispolarized or converted by PBS (Polarization-Beam Splitter) forseparation into respective color light of red, green, and blue (R/G/B).Each separated color light is directed into each liquid crystal panelcorresponding thereto, and optically modulated by the liquid crystalpanel in accordance with a video signal. Each optically modulated colorlight is combined by a cross dichroic prism and projected onto a screenthrough a projection optical system.

In this event, a liquid crystal panel which operates in a TN (TwistedNematic) mode can treat only a particular linearly polarized component,so that each color light is coordinated in a predetermined polarizationdirection (for example, S-polarization) by a polarizing plate before itimpinges on the liquid crystal panel, and then optically modulated bythe liquid crystal panel. Subsequently, an S-polarized component is cutby a polarizing plate on the exit side of the liquid crystal panel toextract a P-polarized component alone.

In this way, within a liquid crystal unit which includes anincident-side polarizing plate, a liquid crystal panel, and an exit-sidepolarizing plate, the incident-side polarizing plate and exit-sidepolarizing plate disposed before (upstream) and after (downstream) theliquid crystal panel along the optical axis each have functions ofpassing only polarized light in one axial direction and blocking otherpolarized light, and therefore generate heat during their operations dueto light absorption. Also, the liquid crystal panel internally generatesheat during its operations in the same manner because part of thetransmitted light is blocked by a black matrix disposed on boundaries ofrespective pixels.

Organic materials are often used for these liquid crystal panels andpolarizing plates, so that if they are irradiated with light at shortwavelengths or are exposed to high temperatures for a long time, theirfunctions will be largely compromised by damaged alignment films of theliquid crystal panels, lower polarization selection characteristics ofthe polarizing plates, and the like. Accordingly, countermeasures toheat radiation, such as forced air cooling, are required for thesecomponents of the liquid crystal unit.

A specially configured cooling apparatus is required for efficientlycooling a plurality of heat generating spots of a plurality ofcomponents in an electronic device, each of which has surfaces thatoppose each other with a spacing defined therebetween, and includes heatgenerating spots on the surfaces opposite to each other.

FIGS. 1( a) and 1(b) are schematic diagrams of the configuration of aliquid crystal projector apparatus of a background related art, whereFIG. 1( a) generally illustrates the appearance of the general liquidcrystal projector apparatus, and FIG. 1( b) illustrates the internalstructure of the liquid crystal projector apparatus. FIG. 2 in turn is aschematic diagram of the internal configuration of the liquid crystalprojector apparatus.

As mainly illustrated in FIG. 2, liquid crystal projector apparatus 1includes cooling fan 3 for forcedly cooling liquid crystal unit 2, andcooling air duct 4, both of which are mounted in the housing of liquidcrystal projector apparatus 1. In addition, lamp cooling fan 7 forcooling light source 5, power supply unit 10 and the like, exhaust fan 9for exhausting the housing, and the like are provided as required.

Here, a general method of cooling liquid crystal unit 2 of liquidcrystal projector apparatus 1 will be described with reference to FIGS.3A and 3B. FIGS. 3A and 3B are schematic diagrams illustrating theconfiguration of a cooling unit for cooling the liquid crystal unit inthe liquid crystal projector apparatus, where FIG. 3A is an explodedperspective view, and FIG. 3B is a schematic cross-sectional view fordescribing a forced air cooling operation.

In FIG. 3B, liquid crystal unit 2 including incident-side polarizingplate 12, liquid crystal panel 13, and exit-side polarizing plate 14 isprovided for each color light (R/G/B), and air cooling device 15including cooling fan 3 and cooling air duct 4 is disposed therebelow.

During the operation of air cooling device 15, air 16 from cooling fan 3is fed into spaces among incident-side polarizing plate 12, liquidcrystal panel 13, exit-side polarizing plate 14, which include eachliquid crystal unit 2, from the lower end of liquid crystal unit 2through discharge port 17 provided in cooling air duct 14 to performforced air cooling.

In recent years, a reduction in size and an increase in luminance havebeen increasingly requested for liquid crystal projector apparatuses inaccordance with their versatile usages. To respond to such requests, anincrease in lamp power and a reduction in size of display device are nowunder progress, resulting in an increase in flux density of lightincident on the liquid crystal unit, and a continuous increase in heatload on each component which forms part of liquid crystal unit 2.

For example, in a liquid crystal projector apparatus (1.0″-XGA) of2000-lm class, a total amount of heat generated by liquid crystal unitsis approximately 15 W, while heat flux of an exit-side polarizing plateis approximately 0.6 W/cm². However, with a 5000-lm class, a totalamount of heat generated by liquid crystal units amounts to 35 W ormore, while heat flux of an exit-side polarizing plate amounts to 1.4W/cm² or more.

Generally, when forced air cooling is used for cooling liquid crystalunits, the amount of air fed by a fan is increased to enhance the airvelocity around a heat generating spot to improve the heat transfercoefficient and heat radiation capabilities, thereby accommodating everincreasing heat loads.

However, as the amount of fed air is increased by increasing therotational speed of the fan, operation noise will increase. On the otherhand, as the amount of fed air is increased by employing a fan of largersize, this mitigates reducing the size of the apparatus.

On the other hand, requests have been gradually increased for longerlifetime of liquid crystal projector apparatus for reducingenvironmental loads and running cost. Apart from lamps, a factor whichdominates the lifetime of the liquid crystal projector apparatus ismainly the lifetime due to degraded optical characteristics in theliquid crystal units. Accordingly, the lifetime can be increased byreducing the operating temperature of the liquid crystal units throughimprovements on the cooling performance.

However, in a laminar flow region, the average heat transfer coefficientof forced convection is proportional to the square root of the airvelocity, while the operating temperature of the panel is reciprocallyproportional to the square root of the air velocity. Thus, a reductionin the operating temperature of the panel to some extent will result ina lower sensitivity of a change in panel temperature to a change in airvelocity.

FIG. 4 is a graph showing the relationship between a panel cooling airvelocity and the panel operating temperature in 0.8″-SXGA (5000-lmclass, 25° C. environment). For reducing the panel operating temperaturefrom 70° C. to 60° C. (ΔT=31 10° C.), the air velocity may be simplyincreased from 4.5 m/s to 8 m/s (ΔV=+3.5 m/s), whereas for reducing from60° C. to 50° C. (ΔT=−10° C.), the air velocity must be increased from 8m/s to 18 m/s (ΔV=+10 m/s), as can be seen from the graph.

In this way, when forced air cooling is relied on to further reduce thepanel operating temperature for prolonging the lifetime, the cooling airvelocity is excessively required as the target temperature is lower.Accordingly, the fan operation noise can further increase, or theapparatus can be increased in size, as described above, and in somecases, the limit of cooling capabilities (air cooling limit) can beexceeded, so that the development of a highly efficient liquid crystalunit cooling system is an urgent necessity.

Further, in regard to the liquid crystal panel, another requirementexists for cooling from a viewpoint of image quality. Specifically,since the optical modulation effect to an input signal highly depends onthe temperature in the optical modulation of the liquid crystal panel,thermal gradient on the panel plane cause variations in luminance andcolor, resulting in a degraded quality of projected images. For thisreason, in cooling the liquid crystal panel, a cooling method is desiredto minimize a temperature gradient and temperature variations whichoccur on the surface of the panel in operation.

FIG. 5 is a schematic side view illustrating a first related art exampleof liquid crystal unit cooling, as disclosed in Patent Document 1(JP-11-295814A). Specifically, an apparatus for improving a liquidcrystal panel cooling efficiency is provided with the aid of airdirecting plate 39 disposed below cross dichroic prism 35 to optimizethe direction of air fed from cooling fan 3.

FIG. 6 is a schematic perspective view illustrating a second related artexample of liquid crystal unit cooling, as disclosed in Patent Document2 (JP-2001-318361A). Specifically, an apparatus for improving a coolingefficiency is provided with protrusion 41 for guiding cooling air toliquid crystal holding frame 40 to restrain interstices of air fed fromduct discharge port 42.

FIG. 7 is a schematic cross-sectional view illustrating a third relatedart example of liquid crystal unit cooling, as disclosed in PatentDocument 3 (JP-2004-61894A). Specifically, an apparatus is provided foradjusting a cooling air velocity by changing air passage widths (X and Yin the figure) between liquid crystal panel 13 and polarizing plate 14with the provision of cutout 43 in an air passage of liquid crystalpanel holding frame 40.

FIGS. 8A and 8B are schematic diagrams illustrating a first example of afourth related art example of liquid crystal unit cooling, where FIG. 8Ais a top plan view, and FIG. 8B is a lateral sectional view. FIGS. 9Aand 9B are schematic diagrams illustrating a second example of thefourth related art example of liquid crystal unit cooling, where FIG. 9Ais a top plan view, and FIG. 9B is a lateral sectional view. This fourthrelated art example is disclosed in Patent Document 4 (JP-2000-124649A).

In FIGS. 8A and 8B, air leading plate 44 having a U-shaped groove formis connected (positioned) between liquid crystal panel 13 and polarizingplate 12, for turning the direction of cooling air blown up from belowon the exit side of liquid crystal panel 13 by the U-shaped groove atthe upper end by 180° to feed the air from above to below on incidentpolarizing plate 12, thereby eliminating thermal gradient which occur onthe panel surface.

On the other hand, in FIGS. 9A and 9B, an apparatus is disclosed foreliminating thermal gradient on a panel plane with the provision of apair of cooling fans 3 a, 3 b above and below liquid crystal panel 13,with the liquid crystal panel interposed therebetween, to feed an airstream from below to above on the exit side and from above to below onthe incident side.

FIG. 10 is a schematic lateral sectional view illustrating a fifthrelated art example of liquid crystal unit cooling. This fifth relatedart example is disclosed in Patent Document 5 (JP-2001-209126A) whichdiscloses an apparatus which includes a liquid crystal panel coolingunit in a closed internal circulation structure with the use ofcirculation duct 45, where first cooling fan 3 a air-cools a liquidcrystal unit, exhaust air heated by received heat is transferred toexternal air circulation duct 46 shield by circulation duct 45 through aheat sink or the like (not shown, provided on the boundary ofcirculation duct 45 and air circulation duct 46 in the figure), and theheat of the heat sink is radiated by second cooling fan 3 b which isprovided outside.

DISCLOSURE OF THE INVENTION Problems to be Solved by the Invention

As described above, when an attempt is made to increase the air velocityof the fan to improve the cooling performance in the cooling of theliquid crystal unit, this will lead to increased fan operation noise andmounting volume. Further, when the liquid crystal unit is desirablycooled to about room temperature to prolong its lifetime, this can behampered by the air cooling limit (the temperature is not reduced evenif the air velocity is increased).

Patent Document 1 (first related art example) discloses a structurewhich includes an air directing plate below a cross dichroic prism foradjusting the direction of cooling air fed to a liquid crystal panel toimprove the efficiency of cooling the liquid crystal panel. However,even if an increased amount of air is fed to impinge the panel exit sideby optimizing the angle at which the air is fed to the liquid crystalpanel, a reduced air stream is fed to the exit-side polarizing platepositioned on the opposite surface thereof on the contrary, therebyresulting in a lower efficiency of cooling the exit-side polarizingplate.

Patent Document 2 (second related art example) discloses an apparatuswhich includes a protrusion in a liquid crystal panel holding frame forlimiting interstices of fed air stream to efficiently guiding the airstream fed through the duct to the liquid crystal panel without waste.However, since the restraint of leaking air by the protrusion partiallycauses a reduction in air velocity due to an increased air resistance,and a rise in panel temperature due to stagnation of discharge heat(exacerbation of release of exhaust air) in a downstream region (abovethe liquid crystal panel), the improvement on the cooling efficiency iscanceled out, thus making it difficult to provide sufficient effects.

Patent Document 3 (third related art example) discloses an apparatuswhich includes a cutout in an air path of a liquid crystal panel holdingframe to ensure an air passing area even if a spacing with a polarizingplate is narrow, thereby compensating for the cooling air velocity.However, when the spacing between respective units is narrow at aninflow end, this constitutes an air resistance to reduce the amount offed air. Also, even if a cutout is provided on the downstream sidethereof to increase the air passing area, the air velocity is reduced atcooled components (liquid crystal panels, and light transmission planesof polarizing plates), so that the cooling efficiency is not increased.

The first example of Patent Document 4 (fourth related art example)discloses a structure which includes an air guiding plate having aU-shaped groove form connected (positioned) between a liquid crystalpanel and a polarizing plate to turn around an air stream fed by a fanat a top end to cool the liquid crystal panel in opposite directions onthe incident side and exit side of the liquid crystal panel, therebyalleviating variations in panel temperatures. In this event, however,the air passing area is reduced to one half, and an air travelingdistance is increased twice, as compared with conventional structures,thus exacerbating the air resistance to restrain the amount of air fedby the fan. Also, since the air which has passed by and cooled the panelexit side in the former half of the U-shaped groove is heated bydischarged heat, the heat radiation capabilities significantly decreasein the latter half in which the air turns around to pass by the panelincident side. Thus, this structure is not suitable for highly efficientcooling.

On the other hand, in the second example (FIGS. 9A an 9B) of the fourthrelated art example which ventilates the panel incident side and exitside individually in opposite directions using a pair of fans, this iseffective in that the heat generation distributions (cooling actions) onthe panel surfaces are upside down on the incident side and exit side tobalance the temperature within the panel. However, this structurefollows a conventional cooling method in that a parallel air flow isdirected onto a heat generating plane to radiate heat, and fails toachieve a sufficient cooling efficiency because an air resistanceincreases due to a reduction of each air passing area to one half whilea heat radiation load per fan is reduced.

Patent Document 5 (fifth related art example) forcedly air-cools liquidcrystal units by a closed circulation system to transfer heat of exhaustair to the outside through a heat sink and radiate the heat by anotherair-cooling fan, thereby reducing the temperature of internallycirculated air for cooling the liquid crystal units. In this event,however, while effective for preventing dusts being introduced into theliquid crystal units, the transport of discharged heat involves a heattransfer process of gas (internally circulated flow) --> solid (heatsink)--> air (forced air cooling to external air) twice, and thereforethe fifth related art example disadvantageously suffers from a poor heattransport efficiency due to a large heat resistance from the internallycirculated air to the external air and cannot be applied to a highluminance model which generates a large amount of heat.

It is an exemplary feature of the present invention to provide a silentcooling apparatus for effectively reducing the operating temperature ofan electronic device which includes a plurality of components whichinclude surfaces opposite to each other with a spacing therebetween andhave a heat generating spot on at least any of the surfaces opposite toeach other, in a small and low-cost configuration.

MEANS FOR SOLVING THE PROBLEM

An apparatus for cooling a heat generating spot of an electronic deviceof the present invention is a cooling apparatus for forcedly air-coolinga heat generating spot of an electronic device which includes aplurality of components which are disposed side-by-side to have the samein-plane direction, and which include heat generating spots within theirsurfaces. The cooling apparatus further includes first air cooling meansfor feeding an air stream to the heat generating spot in an orientationof the in-plane direction, and second air cooling means for feeding anair stream to the heat generating spot in the in-plane direction in adifferent orientation from the air stream by the first air coolingmeans.

EFFECTS OF THE INVENTION

In the apparatus for cooling a heat generating spot of an electronicdevice in the present invention, for example, when applied to a coolingmechanism for a liquid crystal image display, a pair of air coolingmeans disposed in opposition in the vertical direction across a liquidcrystal unit interposed therebetween, are used to cause air streams tocollide in an opposing state in a space between a liquid crystal paneland a polarizing plate, thereby generating an impinging jet flowperpendicular to each heat generating plane of the liquid crystal paneland polarizing plate. In this way, the heat transfer coefficient can besignificantly improved to promote the heat transfer, as compared withthe cooling of a liquid crystal unit according to the background relatedart which relies on a uniform flow along a parallel plane, thusadvantageously providing small-size, low-cost, and low-noise highlyefficient cooling.

BRIEF DESCRIPTION OF THE DRAWINGS

The foregoing and other exemplary purposes, aspects and advantages willbe better understood from the following detailed description of anexemplary embodiment of the invention with reference to the drawings.

FIG. 1( a) and FIG. 1( b) are schematic diagrams of the configuration ofa liquid crystal projector apparatus of a background related art, whereFIG. 1( a) illustrates the appearance of a general liquid crystalprojector apparatus, and

FIG. 1( b) illustrates the internal structure of the liquid crystalprojector apparatus.

FIG. 2 illustrates a schematic diagram illustrating the internalconfiguration of a liquid crystal projector apparatus.

FIG. 3A illustrates a schematic exploded perspective view illustratingthe configuration of a cooling unit for a liquid crystal unit of aliquid crystal projector apparatus.

FIG. 3B illustrates a schematic cross-sectional view for describing aforced air cooling operation of the cooling unit for the liquid crystalunit of the liquid crystal projector apparatus.

FIG. 4 illustrates a graph showing the relationship between a panelcooling air velocity and a panel operating temperature in 0.8″-SXGA(5000-lm class: 25° C. environment).

FIG. 5 illustrates a schematic side view illustrating a first relatedart example of cooling a liquid crystal unit.

FIG. 6 illustrates a schematic perspective view illustrating a secondrelated art example of cooling a liquid crystal unit.

FIG. 7 illustrates a schematic side view illustrating a third relatedart example of cooling a liquid crystal unit.

FIG. 8A illustrates a schematic top plan view illustrating a firstexample of a fourth related art example of cooling a liquid crystalunit.

FIG. 8A illustrates a schematic lateral sectional view illustrating thefirst example of the fourth related art example of cooling a liquidcrystal unit.

FIG. 9A illustrates a schematic top plan view illustrating a secondexample of the fourth related art example of cooling a liquid crystalunit.

FIG. 9B illustrates a schematic lateral sectional view illustrating thesecond example of the fourth related art example of cooling a liquidcrystal unit.

FIG. 10 illustrates a schematic lateral sectional view illustrating afifth related art example of cooling a liquid crystal unit.

FIG. 11 illustrates a schematic exploded perspective view of anapparatus for cooling a heat generating spot of a liquid crystal imagedisplay according to a first exemplary embodiment of the presentinvention.

FIG. 12 illustrates a schematic cross-sectional view for describing theconfiguration and operation of the apparatus for cooling a heatgenerating spot in a liquid crystal image display according to the firstexemplary embodiment of the present invention.

FIG. 13 illustrates a schematic partial cross-sectional view and apartially enlarged cross-sectional view showing the flow of an airstream for cooling a liquid crystal unit in FIG. 12.

FIG. 14 illustrates a schematic cross-sectional view for describing theconfiguration and operation of apparatus for cooling a heat generatingspot in a liquid crystal image display according to a second exemplaryembodiment of the present invention.

FIG. 15 illustrates a schematic partial cross-sectional view and apartially enlarged cross-sectional view showing the flow of an airstream for cooling a liquid crystal unit in FIG. 14.

FIG. 16A illustrates a schematic cross-sectional view of a coolingstructure in the first exemplary embodiment, as viewed from a lighttransmission plane side.

FIG. 16B illustrates a schematic cross-sectional view of the coolingstructure in the first exemplary embodiment, as viewed from a transverseplane side.

FIG. 16C illustrates a schematic cross-sectional view of a coolingstructure in a third exemplary embodiment, as viewed from a lighttransmission plane side.

FIG. 16D illustrates a schematic cross-sectional view of a coolingstructure in a fourth exemplary embodiment, as viewed from a lighttransmission plane side.

FIG. 16E illustrates a schematic cross-sectional view of a coolingstructure in a fifth exemplary embodiment, as viewed from a lighttransmission plane side.

FIG. 16F illustrates a schematic cross-sectional view of a coolingstructure in a sixth exemplary embodiment, as viewed from a lighttransmission plane side.

FIG. 17A illustrates a schematic explanatory diagrams of a seventhexemplary embodiment according to the present invention, including aperspective view which describes a duct configuration of a coolingapparatus, and a cross-sectional view which describes operations.

FIG. 17B illustrates a schematic explanatory diagram of the seventhexemplary embodiment according to the present invention, and a top planview which describes the operation of the cooling apparatus.

FIG. 18 illustrates a schematic explanatory diagrams showing a controlmethod in a cooling apparatus of the present invention, where (i)illustrates a front view of a liquid crystal unit as viewed from a lighttransmission plane side, and (ii) illustrates a cross-sectional view ofthe same, and (a), (b), (c) show changes in the amount of air streams ofa fan in time series.

FIG. 19 illustrates a schematic diagram for describing impinging jetcooling.

FIG. 20A illustrates a schematic diagram for describing a liquid crystalpanel and a light transmission plane of a polarizing plate in a liquidcrystal image display, and a front view which depicts a liquid crystalpanel and a polarizing plate side by side.

FIG. 20B illustrates a schematic diagram for describing a liquid crystalpanel and a light transmission plane of a polarizing plate in a liquidcrystal image display, and a side view which displays a liquid crystalpanel and a polarizing plate side by side.

BEST MODE FOR CARRYING OUT THE INVENTION

Next, an apparatus for cooling a heat generating spot of an electronicdevice according to an exemplary embodiment of the present inventionwill be described in terms of the configuration and operation withreference to the drawings. In this exemplary embodiment, forfacilitating the understanding, the electronic device will be describedas represented by a liquid crystal image display of a liquid crystalprojector apparatus, and components such as an incident-side polarizingplate, a liquid crystal panel, and an exit-side polarizing plate whichform a liquid crystal unit. However, the present invention is notlimited to this exemplary embodiment, but may also be applied to acooling apparatus or the like for an electronic device which includes aplurality of components, each of which includes surfaces opposite toeach other with a spacing defined therebetween, where at least any ofthe surfaces opposite to each other is a heat generating spot, forexample, heat generating spots disposed across a narrow gap, such as arack unit which has a plurality of printed circuit boards mountedtherein in parallel, IC chips mounted on a board of a small-sizeelectronic device in a narrow space facing an inner wall of a housing,and the like.

Since the liquid crystal projector apparatus has been previouslydescribed in the section of Background Art, the description is omittedhere.

FIG. 11 is a schematic exploded perspective view of an apparatus forcooling a heat generating spot of a liquid crystal image displayaccording to a first exemplary embodiment of the present invention, FIG.12 is a schematic cross-sectional view for describing the configurationand operation of the heat generating spot cooling apparatus in theliquid crystal image display according to the first exemplary embodimentof the present invention, and FIG. 13 includes a schematic partialcross-sectional view and a partially enlarged cross-sectional viewshowing the flow of air for cooling a liquid crystal unit in FIG. 12.

Cooling apparatus 26 a for a liquid crystal image display (electronicdevice) of a liquid crystal projector apparatus according to the presentinvention is formed of first air cooling unit 29 a including firstcooling fan 27 a and first air cooling duct 28 a, and like second aircooling unit 33 a including second cooling fan 31 a and second aircooling duct 32 a, disposed at an upper and a lower end of liquidcrystal unit 2 which is provided for each of R/G/B color light andincludes incident-side polarizing plate 12, liquid crystal panel 13, andexit-side polarizing plate 14 which are assembled into a unit.

Referring next to FIG. 12, operations for cooling liquid crystal unit 2by cooling apparatus 26 a in this exemplary embodiment, will bedescribed.

In this exemplary embodiment, as illustrated in FIG. 12, first aircooling unit 29 a is provided at the lower end of liquid crystal unit 2,and first air stream 30 a generated from first cooling fan 27 a passesthrough spaces between incident-side polarizing plate 12 and liquidcrystal panel 13 of each color light and between liquid crystal panel 13and exit-side polarizing plate 14 from below to above through first aircooling duct 28 a.

Additionally, second air cooling unit 33 a is provided at the upper endof liquid crystal unit 2, and second air stream 34 a generated fromsecond cooling fan 31 a passes through spaces between incident-sidepolarizing plate 12 and liquid crystal panel 13 of each color light andbetween liquid crystal panel 13 and exit-side polarizing plate 13 fromabove to below through second air cooling duct 32 a in the same manner.

Referring next to FIG. 13, a description will be given of a coolingaction by cooling apparatus 26 a in this exemplary embodiment. FIG. 13is a schematic cross-sectional view of liquid crystal unit 2 for onecolor light alone, extracted from among liquid crystal units 2 in FIG.12.

As described above, first air stream 30 a is sent from the lower end ofliquid crystal unit 2 into the space between incident-side polarizingplate 12 and liquid crystal panel 13 and the space between liquidcrystal panel 13 and exit-side polarizing plate 14 from below to above.Second air stream 34 a is sent from the upper end of liquid crystal unit2 into the space between incident-side polarizing plate 12 and liquidcrystal panel 13 and the space between liquid crystal panel 13 andexit-side polarizing pate 14 from above to below in the same manner.First and second air streams 30 a and 34 a collide at a central position(impinging plane a in the drawing) in an opposing state in a spacebetween the respective units when first cooling fan 27 a and secondcooling fan 31 a have an equivalent amount of fed air, and when firstair cooling duct 28 a and second air cooling duct 32 a have an equal airresistance.

In this event, first air stream 30 a and second air stream 34 a whichcollide in an opposing state from directions opposite to each other,generate evolutional flows which perpendicularly go to polarizing plates12, 14 on the incident/exit sides and the light transmission plane ofliquid crystal panel 13 at positions at which they collide, asillustrated in a detailed view of FIG. 13. Thus, a perpendicular jetstream is formed toward a heat generating plane (light transmissionplane) while allowing the transmission of the color light.

In this way, the heat transfer coefficient can be largely increased ascompared with a cooling method of the background related art whichrelies on a parallel flat flow, thus making it possible to cool theliquid crystal units at a high heat radiation efficiency.

Next, a second exemplary embodiment in an apparatus for cooling anelectronic device according to the present invention will be describedin detail with reference to the drawings. FIG. 14 is a schematiccross-sectional view for describing the configuration and operation ofthe apparatus for cooling a heat generating spot in a liquid crystalimage display according to the second exemplary embodiment of thepresent invention, and FIG. 15 includes a schematic partialcross-sectional view and a partially enlarged cross-sectional viewshowing the flow of air for cooling a liquid crystal unit in FIG. 14.

In cooling apparatus 26 b in the second exemplary embodiment, and incooling apparatus 26 a in the first exemplary embodiment, second aircooling unit 33 b disposed at the upper end of liquid crystal unit 2includes axial fan 36 alone.

Also, in this event, first air flow (stream) 30 b sent by first aircooling unit 29 b including first cooling fan 27 b and first air coolingduct 28 b, and second air stream 34 b sent from second air cooling unit33 b including axial fan 36 are fed into the space between incident-sidepolarizing plate 12 and liquid crystal panel 13, which form part ofliquid crystal unit 2, and the space between liquid crystal panel 13 andexit-side polarizing plate 14. Hence, the first air flow 30 b and thesecond air stream 34 b collide at substantially the central positionbetween the respective elements (collision plane b in FIG. 15) in anopposing state. Thus, a perpendicular jet stream is generated which goestoward incident/exit-side polarizing plates 12, 14 and the lighttransmission plane of liquid crystal panel 13, which are heat generatingplanes, in a manner similar to the first exemplary embodiment describedabove.

In this exemplary embodiment, the second air cooling unit includes theaxial fan alone, thereby reducing the size and simplifying the mounting.

Next, third to sixth exemplary embodiments in the apparatus for coolingan electronic device according to the present invention will bedescribed with reference to the drawings.

FIGS. 16A to 16F are schematic cross-sectional views of coolingstructures in the first and third to sixth exemplary embodiments, whereFIG. 16A is a schematic cross-sectional view of the first exemplaryembodiment as viewed from a light transmission plane side; FIG. 16B is aschematic cross-sectional view of the first exemplary embodiment asviewed from a transverse plane side; FIG. 16C is a schematiccross-sectional view of a third exemplary embodiment as viewed from thelight transmission plane side; FIG. 16D is a schematic cross-sectionalview of a fourth exemplary embodiment as viewed from the lighttransmission plane side; FIG. 16E is a schematic cross-sectional view ofa fifth exemplary embodiment as viewed from the light transmission planeside; and FIG. 16F is a schematic cross-sectional view of a sixthexemplary embodiment as viewed from the light transmission plane side.FIGS. 16A and 16B are provided for describing a comparison of the firstexemplary embodiment with the third to sixth exemplary embodiments.

In the first exemplary embodiment, air streams are fed by independentair cooling units 29 a, 33 a from the upward and downward directions ofliquid crystal unit 2 in opposing directions to cause cooling airstreams to collide with each other at the central position on the lighttransmission plane (collision plane a) of liquid crystal unit 2, therebygenerating a perpendicular flow (collision jet stream) toward each heatgenerating plane.

On the other hand, in the cooling structure in the third exemplaryembodiment illustrated in FIG. 16C, first discharge port 37 c of firstair cooling unit 29 c disposed at the lower end of liquid crystal unit2, and second discharge port 38 c of second air cooling unit 33 cdisposed at the upper end of liquid crystal unit 2 in the same mannerare offset to left and right, respectively, from the central axial lineof the panel indicated by ax in the figure.

In this way, first air stream 30 c by first air cooling unit 29 c andlike second air stream 34 c by second air cooling unit 33 c oppositelycollide at a position corresponding to a shift of an air velocitydistribution, to form evolutional flows which go perpendicularly to theheat generating planes at positions substantially along a diagonal(collision plane c in the figure) on the light transmission plane.Consequently, it is possible to accomplish wide and highly efficientcooling of the liquid crystal unit.

In this event, since the air streams flow in an oblique direction afterthe collision, heated exhaust air can be readily discharged outside ofthe housing such that the exhaust air will not circulate again into thecooling air.

The cooling structure in the fourth exemplary embodiment illustrated inFIG. 16D includes first discharge port 37 d of first air cooling unit 29d and like second discharge port 38 d of second air cooling unit 33 dbeing disposed so as to oppose substantially on a diagonal of the lighttransmission plane.

In this way, like the third exemplary embodiment described above, firstair stream 30 d by first air cooling unit 29 d and like second airstream 34 d by second air cooling unit 33 d are fed into the spacebetween the incident-side polarizing plate and liquid crystal panel, andthe space between the liquid crystal panel and exit-side polarizingplate, and collide in opposition to each other at a diagonal position(collision plane d in the figure) on the light transmission plane. Thus,evolutional flows are formed which go perpendicularly to the heatgenerating planes on the diagonal of the light transmission planes toproduce similar effects to those of the third exemplary embodiment.

The cooling structure in the fifth exemplary embodiment illustrated inFIG. 16E includes in that both first cooling unit 29 e and secondcooling unit 33 e being disposed on both sides of the lower end of theliquid crystal unit. First discharge port 37 e of first air cooling unit29 e and like second discharge port 38 e of second air cooling unit 33 eare set such that air feeding directions intersect on the center line(ax in the figure) of the panel in the vertical direction.

In this event, like other exemplary embodiments, the liquid crystal unitcan be highly efficiently cooled, and simultaneously, the first andsecond air streams can be discharged in the same direction toward abovethe liquid crystal unit, thus facilitating the heat exhaustionprocessing.

The cooling structure in the sixth exemplary embodiment illustrated inFIG. 16F includes first discharge port 37 f of first air cooling unit 29f and like second discharge port 38 f of second air cooling unit 33 fbeing disposed so as to oppose each other on the left and right sides ofliquid crystal unit 2.

In this event, mounting spaces must be provided on the left and rightsides of the liquid crystal units. However, since evolutional flowstoward the heat generating planes are formed on the center axis (ax inthe figure) of the panel, this is effective for a liquid crystal panelwhich exhibits a large temperature gradient in the vertical direction.

Next, a seventh exemplary embodiment in the cooling apparatus of thepresent invention will be described with reference to the drawings.

FIGS. 17A and 17B are schematic explanatory diagrams of the seventhexemplary embodiment according to the present invention, where FIG. 17Aincludes a perspective view which describes a duct configuration of thecooling apparatus, and a cross-sectional view which describes theoperation, while FIG. 17B is a top plan view which describes theoperation in the same manner.

In the seventh exemplary embodiment illustrated in FIGS. 17A and 17B,the second cooling fan which forms part of the second air cooling unitis omitted. However, first cooling fan 27 g is shared, and second aircooling duct 32 g is branched halfway from first air cooling duct 28 g,and extended toward the center of liquid crystal unit 2 at a lateralposition of liquid crystal unit 2 to discharge second air stream 34 gtoward the center of the light transmission plane substantiallyhorizontally from a lateral direction of liquid crystal unit 2, in thecooling apparatus of the first to sixth exemplary embodiments describedabove.

In this way, first air stream 30 g fed by first duct 28 g from below toabove liquid crystal unit 2, and second air stream 34 g fed from oneside of liquid crystal unit 2 have two different vectors (orthogonalvectors in this exemplary embodiment) and collide in a space in the unitnear the central position on the light transmission plane betweenincident-side polarizing plate 12 and liquid crystal panel 13 or betweenliquid crystal panel 13 and exit-side polarizing plate 14. Thus, a highcooling effect can be accomplished in a manner similar to the first tosixth exemplary embodiments described above.

Also, in this event, since first cooling fan 27 g is shared by first aircooling duct 28 g and second cooling duct 32 g, the number of mountedfans can be reduced to lead to a reduction in cost and noise. Inaddition, since second duct 32 g is formed by branching part of firstduct 30 g, not only the cooling fan but also the cooling apparatus canbe reduced in mounting volume, thus facilitating applications to smallprojector apparatuses.

Further, since either the second cooling fan or the second duct need notbe provided as an independent member, an assembling process can besimplified. This additionally allows maintaining the same productivityas the projector apparatus in the configuration of the backgroundrelated art which employs a single cooling fan, while providing highcooling capabilities.

Next, with reference to the drawings, described is a method of improvingthe quality of projected image using the cooling apparatus of thepresent invention by expanding a cooling action area to increase a heatradiation effect and simultaneously mitigating thermal gradient on thesurface of the liquid crystal panel.

FIG. 18 includes schematic explanatory diagrams showing a control methodin the cooling apparatus of the present invention, where (i) is a frontview of a liquid crystal unit as viewed from the light transmissionplane side, and (ii) illustrates a cross-sectional view of the same, and(a), (b), (c) indicate changes in time-series fan air amount. The order(a) --> (b) --> (c) --> (b) --> (a) represents fan air amount control intime-series and a ventilation state at the respective instances.

In the explanatory diagrams, the cooling apparatus of the firstexemplary embodiment described above is given as an example, but it canbe applied to cooling apparatuses of other exemplary embodiments.

First air cooling unit 29 a and second air cooling unit 33 a provided atthe lower end and upper end of liquid crystal unit 2, respectively,include a first cooling fan (not shown) and first air cooling duct 28 a,and a second cooling fan (not shown) and second air cooling duct 32 a,respectively. From respective duct discharge ports, first air stream 30a and second air stream 34 a are fed in opposite directions into spacesbetween incident-side polarizing plate 12 and liquid crystal panel 13and between liquid crystal panel 13 and exit-side polarizing plate 14.Streams 30 a, 30 b collide at midway positions therein to formevolutional flows in a direction perpendicular to the light transmissionplanes. Thus, the heat generating planes are cooled with perpendicularjet streams.

This cooling method controls the ratio of the amount of air fed by thefirst cooling fan to the amount of air fed by the second cooling fan tovary the location of the collision over time, and move the perpendicularflows to the light transmission planes in the vertical direction,thereby expanding an area to which the highly efficient cooling acts,and simultaneously mitigating the difference in temperature on the panelsurface.

Specifically, the independent cooling fans (first cooling fan and secondcooling fan) are controlled to adjust the ratio of the respectiveamounts of air fed by the fans such that a first air amount is largerthan a second air amount at a certain time (FIG. 18( a)); such that thefirst air amount is equal to the second air amount at the next time(FIG. 18( b)); and such that the first air amount is smaller than thesecond air amount at the next time (FIG. 18( c)). The air amount controlmay electrically vary the rotational speeds of the fans, or may beconducted by adjusting the openings of dampers provided in the ducts.

The control is periodically repeated such as (a) --> (b) --> (c) --> (b)--> (a), thereby vertically moving the evolutional flows (collision jetstreams) formed on the input/output polarizing plates and the lighttransmission plane of the liquid crystal panel to vary the position atwhich the maximum cooling effect is provided (i.e., the position atwhich the air streams collide) to expand a region in which the coolingaction is high, and mitigate local variations in heat transfercoefficient within the light transmission plane over time, so that thetemperature gradient is restrained within the panel surface to improvethe quality of projected images.

While the foregoing description has given the first exemplary embodimentas an example, it is obvious that similar effects are also provided byconducting such air amount control in other exemplary embodiments.

In an eighth exemplary embodiment of an apparatus for cooling a heatgenerating spot of an electronic device of the present invention, afirst air stream from first air cooling means and a second air streamfrom a second air cooling means have different air velocity vectors fromeach other. The first air cooling means and second air cooling means maybe set such that the first air stream and second air stream collide witheach other at the positions of heat generating spots on opposingsurfaces of a plurality of components. The first air cooling means maybe disposed at the lower end of the opposing planes of the plurality ofcomponents, while the second air cooling means may be disposed at theupper end of the opposing planes of the plurality of components. Thefirst air cooling means may include a first cooling fan and a first aircooling duct, while the second air cooling means may include a secondair cooling fan and a second air cooling duct. One of the first aircooling means and second air cooling means may include a cooling fan andan air cooling duct, while the other may include a cooling fan alone.The first air cooling means may include a first cooling fan and a firstair cooling duct, while the second air cooling means may include thefirst cooling fan shared by the first air cooling means, and a secondair cooling duct branched halfway from the first air cooling duct forfeeding air into the plane from a direction different from an airfeeding direction of the first air cooling duct. Also, the first coolingfan and second cooling fan may provide variable amounts of air.

The effect of the present invention can also be produced in the coolingof heat generating spots in a plurality of components of an electronicdevice which have surfaces opposite to each other, at least any of whichincludes the heat generating spot.

Also, since the position at which fan air streams collide can bearbitrarily set by arbitrarily controlling the ratio of air amounts froma pair of air cooling means, the position at which the collision jetstreams are produced can be periodically varied on the basis of thecenter of the panel to mitigate thermal gradient on the panel surface,thus advantageously improving the image quality.

In a ninth exemplary embodiment of the apparatus for cooling a heatgenerating spot of an electronic device according to the presentinvention, the electronic device may be a liquid crystal image display,and components may include an incident-side polarizing plate, a liquidcrystal panel, and an exit-side polarizing plate which form part of theliquid crystal unit.

In a tenth exemplary embodiment of the present invention, a method ofcooling a heat generating spot of an electronic device may be a heatgenerating spot cooling method for the aforementioned apparatus forcooling a heat generating spot of an electronic device. The tenthembodiment may include feeding a first air stream by first air coolingmeans for components of the electronic device in a first direction ingaps between opposing surfaces of the components. Additionally, a secondair stream is fed by second air cooling means in a second directiondifferent from the first direction in gaps between the opposing surfacesof the components to cause the first air stream and second air stream tocollide with each other near the central positions of heat generatingspots on the opposing surfaces of the component. Thus, evolutional flowsare generated which go perpendicularly to one or both of the opposingsurfaces of the components.

In a method of cooling a heat generating spot of an electronic deviceaccording to an eleventh exemplary embodiment of the present invention,first air cooling means is disposed at a lower end of components of anelectronic device, and second air cooling means is disposed at an upperend of the components of the electronic device. A first air stream bythe first air cooling means may be fed from below to above in spacesbetween a plurality of components, while a second air stream by thesecond air cooling means may be fed cooling below in the spaces betweenthe plurality of components, to cause the first air stream and secondair stream to collide with each other near the central positions of heatgenerating spots on opposing surfaces of the components. Thus,evolutional flows are generated which go perpendicularly to one or bothof the opposing surfaces of the components. By varying, over time, theratio of air amounts of the first cooling fan which forms part of thefirst air cooling means to a second cooling fan which forms part of thesecond air cooling means, the position at which the first air stream andsecond air stream collide may be periodically moved from the centralpositions of the heat generating spots on the opposing surfaces of thecomponents. The electronic device may be a liquid crystal image display,and the components may include an incident-side polarizing plate, aliquid crystal panel, and an exit-side polarizing plate which include aliquid crystal unit.

In a twelfth exemplary embodiment of the present invention, a liquidcrystal projector apparatus includes any of the aforementioned apparatusfor cooling a heat generating spot of an electronic device.

In the apparatus for cooling a heat generating spot of an electronicdevice according to the present invention, when the electronic deviceis, for example, a liquid crystal image display of a liquid crystalprojector apparatus, a pair of independent air cooling means, each,including a cooling fan and an air cooling duct, are provided above andbelow a liquid crystal unit. Thus, air streams are fed across the liquidcrystal unit therebetween from above and below in opposite directions topass the air streams through spaces between the incident-side polarizingplate and liquid crystal panel or between the liquid crystal panel andexit-side polarizing plate. The two air streams to collide near thecenter of a light transmission plane near the central position of a heatgenerating spot to improve the cooling efficiency.

For cooling a heat generating flat plate such as a polarizing plate anda liquid crystal panel by forced air cooling, collision jets cooling maybe given as one of the methods which provides the highest coolingefficiency. FIG. 19 is a schematic diagram for describing the collisionjet cooling. As illustrated in FIG. 19, the collision jet cooling is amethod which involves jetting coolant (air, liquid) 20 perpendicularlyto heat generating flat plate 18 through nozzle 19 to cause an impingingjet flow to collide with heat generating plate 18, thereby radiatingheat from a heat generating plane.

Generally, in the forced air cooling for a heat generating flat plate,two approaches, i.e., a thinning method and a replacement method arecontemplated for improving the heat transfer coefficient to promote theheat transfer.

The former is a method which promotes the heat transfer by reducing thethickness (thinning) of a thermal boundary layer formed on the surfaceof a heat generating body, in which case since the thickness of thethermal boundary layer is reciprocally proportional to the square rootof a the velocity in a main stream direction (flow rate along the flatplate), the aforementioned manner of increasing the air velocity toreduce the temperature of the heat generating body is comparable tothis.

The latter intends to promote the heat transfer by encouraging theexchange of a fluid near the surface of a solid with a fluid slightlyspaced apart therefrom, and is achieved by controlling a turbulent flowwhich is associated with generation/disappearance of a unsteady vortex.

The collision jet cooling for cooling a heat generating flat plate bycausing a jet stream to collide with the heat generating flat plate froma direction perpendicular thereto falls under the latter. The collisionjet cooling demonstrates cooling capabilities higher by a factor of fiveto ten than a conventional method of feeding air along a heat generatingflat plate through a process of:

1) breakage (peeling) of the thermal boundary layer on the surface ofthe heat generating body due to the collision jet stream;

2) exchange of fluids (temperature replacement) due to the evolutionalflow produced on the collision plane; and

3) sliding of the jet stream on the wall due to the Coanda effect (thenature of a fluid by which an object placed in a flow causes a reductionin pressure between a fluid and a wall surface of a solid to attract theflow to the wall surface, thereby changing the direction of the flowalong the object).

Incidentally, when such collision jet cooling is applied, for example,to cooling of a liquid crystal image display in a liquid crystalprojector apparatus, a nozzle position thereof is a problem to besolved. Specifically, since a liquid crystal panel and a polarizingplate generate heat due to a light absorption effect when each colorlight passes, the heat generating plane substantially matches with thelight transmission plane (panel light transmission plane 22, polarizingplate light transmission plane 25), as illustrated in FIGS. 20A and 20B.Accordingly, it is necessary to generate a perpendicular air flow to theheat generating plane so as not to impede the transmission of eachcolor. FIGS. 20A and 20B are schematic diagrams for describing the lighttransmission planes of the liquid crystal panel and polarizing plate ina liquid crystal image display, where FIG. 20A is a front view whichdepicts a liquid crystal panel and a polarizing plate placed side byside, and FIG. 20B is a side view.

Thus, in the cooling mechanism for a liquid crystal image display in thepresent invention, cooling air streams are fed from above and below theliquid crystal unit in directions opposite to each other to cause thecooling air streams to collide with each other near the center of thelight transmission plane in a space between the liquid crystal panel andpolarizing plate. Thus, evolution flows are generated which goperpendicularly to heat generating planes of both the liquid crystalpanel and polarizing plate to form vertical jet streams, therebydramatically increasing the heat transfer coefficient to promote theheat transfer and accomplish highly efficient cooling of the liquidcrystal unit.

Further, by changing the ratio of air amounts by the fans provided aboveand below the liquid crystal unit over time, the position at which theair streams collide (position at which the vertical jet streams aregenerated) can be vertically vibrated from the center of the liquidcrystal panel with respect to the liquid crystal panel and polarizingplate. In this way, since a region at which the maximum cooling effectis demonstrated (position of collision) can be periodically variedwithin the panel surface, it is possible to eliminate thermal gradienton the surface of the liquid crystal panel to improve the quality ofprojected images.

While the invention has been particularly shown and described withreference to exemplary embodiments thereof, the invention is not limitedto these exemplary embodiments. It will be understood by those ofordinary skill in the art that various changes in form and details maybe made therein without departing from the spirit and scope of thepresent invention as defined by the claims.

Further, it is noted that Applicant's intent is to encompass equivalentsof all claim elements, even if amended later during prosecution.

This application is based upon and claims the benefit of priority fromJapanese patent application No. 2006-287395, filed on Oct. 23, 2006, thedisclosure of which is incorporated herein in its entirety by reference.

1. A heat generating spot cooling method for an apparatus for cooling aheat generating spot of an electronic device which comprises a pluralityof components which are disposed side by side to have the same in-planedirection, said components including heat generating spots withinsurfaces thereof, the apparatus comprising: a first air cooling unit forfeeding an air stream to said heat generating spot in an orientation ofthe in-plane direction; and a second air cooling unit for feeding an airstream to said heat generating spot in said in-plane direction in adifferent orientation from the air stream by said first air coolingunit, said method comprising: feeding a first air stream by said firstair cooling unit for said components of said electronic device in afirst direction in the gaps between opposing surfaces of saidcomponents; and feeding a second air stream by said second air coolingunit in a second direction different from the first direction in thegaps between opposing surfaces of said components; and causing saidfirst air stream and said second air stream to collide with each othernear central positions of heat generating spots on opposing surfaces ofsaid components, thereby generating evolutional flows which goperpendicularly to one or both of the opposing surfaces of saidcomponents.
 2. The method of cooling a heat generating spot of anelectronic device according to claim 1, wherein: said first air coolingunit is disposed at a lower end of said components of said electronicdevice, and said second air cooling unit is disposed at an upper end ofsaid components of said electronic device; a first air stream by saidfirst air cooling unit is fed from below to above in a space between aplurality of components; a second air stream by said second air coolingunit is fed from above to below in the space between the plurality ofsaid components; and said first air stream and said second air streamare caused to collide with each other near central positions of heatgenerating spots on opposing surfaces of said components, therebygenerating evolutional flows which go perpendicularly to one or both ofthe opposing surfaces of said components.
 3. The method of cooling aheat generating spot of an electronic device according to claim 1,wherein: the position at which said first air flow collides with saidsecond air flow is periodically moved from the central positions of theheat generating spots on the opposing surfaces of said components byvarying, over time, the ratio of the amount of air fed by said firstcooling fan which forms part of said first air cooling unit to theamount of air fed by said second cooling fan which forms part of saidsecond air cooling unit.
 4. The method of cooling a heat generating spotof an electronic device according to claim 1, wherein: said electronicdevice comprises a liquid crystal image display, and said componentsinclude an incident-side polarizer, a liquid crystal panel, and anexit-side polarizing plate which comprise a liquid crystal unit.